The ability of ultrasound measurements to predict newborn volume and weight will be determined. Two basic methods will be compared: a series of simple measurements combined in a multiple regression against birth weight, and volume measurements made by means of a three-dimensional reconstruction of the fetus as a series of ultrasonic cross sections. The simple measurement to be used are transverse abdominal circumference, skull circumference, biparietal diameter and long axis. The long axis end points and three-dimensional reconstructton will be determined by means of a real-time scanner coupled to a three-dimensional position locating system. Computer programs have been developed which construct a perspective display of scans randomly orientated to each other and which use the reconstruction to find volume. Bench studies on this system have been completed and have shown that the volume estimates are accurate to be better than 10%. If such accuracy can be obtained with the fetus this technique could be used to investigate weekly growth and assess well-being.